Bottom hole assemblies can be run in with a connector at an upper end for later receiving a mating connector to finish a production assembly to the surface. This connector is referred to in the industry as a wet connector. There can be a long delay between when the bottom hole assembly is run in and when the halves of a wet connection are made up. The bottom hole assembly with the lower half of the wet connect and hydraulic lines in between the two are run in with a running tool releasably mated to the lower half of the wet connect. Once the bottom hole assembly is supported at a desired location, the running tool is released from the lower half of the wet connect. Because of hydrostatic pressure at the support location acting on the outside of the control lines against captive atmospheric pressure within the control line there exists a potential for collapse of the control lines due to the differential pressure. One attempt to address this issue is shown in U.S. Pat. No. 6,755,253, where a floating piston is referenced to wellbore hydrostatic on one side and control line internal pressure on the other side for running in. The pressure compensation device in this reference stays with the bottom hole assembly and the floating piston is continually allowed to float even after pressure compensation occurs on running in. The reference does not discuss thermal load compensation at all.
In prior systems at relatively shallow depth of about 2000 meters or less, the developed hydrostatic differentials on the control lines were fairly minimal and there were no attempts to compensate for developed pressures. Similarly at relatively shallow depths the well temperatures were not so great so that thermally induced pressure effects could also be safely ignored. As depths increased to over 10,000 meters failing to compensate for such effect could lead to component damage as the upper half of the wet connect was brought into contact with the lower half and pressure release occurred which could destroy adjacent pressure seals to the erosive aspects of high velocity fluids. At these greater depths the temperatures in the range of 150 degrees Centigrade created pressure effects that required compensation to minimize equipment damage.
The present invention addresses the immediate need for pressure compensation on running in with a pressure compensation system associated with a running tool for the bottom hole assembly. In that way the pressure compensating system is removed with the running tool when it is no longer needed. A thermal compensation system remains with the lower portion of the wet connection during the time between running in and connecting a production string with an upper half of the wet connection at its lower end and control line extending outside the production string to the surface. This time interval can be fairly lengthy in the order of months or even longer. The thermal compensating system uses a lockable piston so that on connection of the production string with the upper portion of the wet connect at its lower end to the lower portion of the wet connect a provision exists to lock the thermal compensation system so that applied control line pressure from the surface can go directly to the tools to be operated without such developed pressure being dissipated due to piston movements for the thermal compensation assembly. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention can be determined from the appended claims.